A344408 - OEIS

%I #13 May 18 2021 04:07:41

%S 40,60,65,85,96,104,105,120,136,140,156,160,165,168,185,192,200,204,

%T 205,220,221,224,232,240,252,260,264,265,273,280,285,288,296,300,305,

%U 312,320,325,336,340,345,348,352,357,360,364,365,377,380,384,385,408

%N Positive discriminants of orders with class number 2.

%C Also positive discriminants of orders with class group isomorphic to C_2.

%C The fundamental terms are listed in A094619.

%H Jianing Song, <a href="/A344408/b344408.txt">Table of n, a(n) for n = 1..10001</a>

%o (PARI) isA344408(d) = (d>0) && !issquare(d) && ((d%4==0)||(d%4==1)) && quadclassunit(d)[2]==[2]

%Y Cf. A133315 (positive discriminants of orders with class number 1), this sequence (class number 2), A344409 (class number 3).

%Y Cf. A322710 (the negative discriminant case), A094619.

%K nonn

%O 1,1

%A _Jianing Song_, May 17 2021